vt100 non-support

[utzoo!decvax!harpo!eagle!mhuxt!cbosg!cbosgd!mark]

The termcap that went out with some 4.1BSD tapes was a mistake - it had
a vt100 entry that was not upward compatible with older programs, and
the version of vi that understood this entry did not go out.  This problem
was corrected long ago but some tapes did go out.

As a quick fix, remove the al and dl entries from your vt100 termcap.
Then, at least vi will work (almost).  It turns out the "eat newline"
glitch of the vt100 is done differently than the c100 (for which it was
designed) and version 3.6 of vi did not handle it.  The fix to this in
3.6 is to (1) make sure your termcap says :xn:, (2) find the two places
in /usr/src/cmd/ex that XN is used, each of which will output an extra
linefeed, (3) change these two pieces of code to output an extra return
before the extra linefeed.  This is tricky - the correct changes will
involve adding another call to the putchar-style routine and making a
compound statement with another pair of {}'s.  (Many people have messed
up this fix by creating a two character "char" constant, or by forgetting
the compound statement.)

Vi version 3.7 knows how to use cs, sc, and rc to get a simulation of
insert/delete line on the vt100.  3.6 did not.

If you run your vt100 with the auto-newline bit set to 0, you should
make sure your termcap does not specify :am: or :xn:.  This configuration
is called vt100-nam in modern termcaps.  The other (recommended) setting
of 1 is called vt100-am.  Both are also known as vt100, enabling a site
to choose a local default.

	Mark